Organic light emitting diode devices (in the following referred to as OLED device or simply OLED) can be made on flexible substrates. One prominent option is to use plastic substrates. Similarly, also other semiconductor devices (in particular organic semiconductor devices) can be provided on flexible substrates. Particular examples are photovoltaic devices and particularly organic photovoltaic devices (OPV).
An advantage of using plastic substrates lies in the possibility of using transparent plastics.
However, a disadvantage of using current plastics lies in that today's flexible plastic substrates do not provide a sufficient moisture barrier and therefore an (additional) encapsulation from the substrate side is needed.
For providing or improving the moisture barrier, a thin-film encapsulation (TFE) is usually employed, consisting of or at least comprising a multilayer stack of inorganic/organic/inorganic materials. At the edge of the TFE, the organic material has to be sealed by at least one inorganic layer (better: inorganic/organic/inorganic stack) to avoid contact with air.
When an OLED, for example, provided on top of such TFE barrier layer on a flexible substrate is cut out of large area plastic substrates or out of the roll that is being used in a roll-to-roll process, the substrate encapsulation is damaged and a leakage path is opened up. In other words, upon cutting through OLEDs on a plastic foil substrate, the TFE barrier layer on the substrate side is damaged, and thus, from the sides, moisture can enter the organic layer. There the H2O molecules will be transported quickly over the whole area. If the moisture reaches, through a pinhole in the inner inorganic layer or the like, the OLED, the access results in a black spot, which will furthermore grow with time.